Art of sandblasting



July 31, 1945.

A. H. EPPLER ART OF SAND BLASTING Filed July 29, 1940 5 Sheets-Sheet 1INVENTOR /7z rm/e H. EPPAEZ MMZWM /ATTORNEYJ".

July 31, 1945. A. H. EPPLER 8 ,7 8

ART OF SAND BLASTING Filed July 29, 1940 3 SheetSSheet 2 INVENTOR HETHUZH.EFF E K ATTORNEY;

M 1 AAA MA A. H. EPPLER 2,380,738

ART OF SAND BLAS'IING Filed July 29, 1940 July 31, 1945.

3 Sheets-Sheet 3 INVENTOR Her/40E H. EPPLEK ATTORN EYS.

7 practical. v

More specifically, it is an object of the inven- Patented July 31,

um'rao STATES PATENT I OFFICE ART OF Arthur H. Eppler, Milwaukee, Wis.applicationllzllz SSH-8 1%. 348,130

word "sand being employed genericallyfor the purposes of thisdescription.

It is the obiect of the invention to provide an improved means andmethod for sand blastin and simultaneously inhibiting the corrosion oroxidation of the freshly cleanedsurface while atthesametimemakingthesandblastmoreef- 1 fective and enabling the use ofcheaper grades of sand than have heretofore been regarded as tion toprovide a sand blasting method and apparatus in which minute quantitiesof a liquid carrier for chemical material are sprayed with thepneumatically propelled sand at the surface to becleaned. In the past ithas been thought necessary for efi'ective high speed sand blasting workto employ special grades of sharp sand entirely free from dust, but inthe .use of my invention I find that I am able to use inexpensive commonsand from practically any source without dust hazard, and to make suchcommon sand out even more rapidy than the best sand heretoforeavailable. It is my theory that the dust present in common sand has inthe methods and apparatus of the prior art operated to cushfion theaction of the sharp particles upon the work. I have found that even aminute proportion of water will not only carry the rust inhibitingchemicals but will minimize the menace of silicosis by laying the dust,and because cheap sand used in my apparatus cuts at least as effectivelyas the highest grade sand in prior art structures, I believe that themist or vapor delivered through the sand blast nomle in my de-; viceaccomplishes this result by segre ating the dust and either increasingits mass and its velocity to match the mass and velocity of the largerparticles, or by removing the dust from the home during intervals whenthe sand is not Btillotheroblectsoftheinventionhavctodo with the mountinof conventional sand blast nouie tips interchangeably on the handleportion of the hostile.

A still further oblect is to obtain the aforesaid advantages while atthe same time sufiiciently moistening the abrasive so as to preclude thebuilding up of a positive magnetic charge upon ferrous metal objectswhich are treated, such a charge being a deterent to machining as wellas to the magnetic fiux testingof the metal. Such a charge is frequentlythe result of dry sand blasting of ferrous metals, It is not present inhydraulic sand blasting but the hydraulic sand blasting has otherdisadvantages avoided by the use of the invention herein disclosed.

Other objects will be apparent to those skilled in the art upon study ofthe following specification of my invention.-

In the drawings:

Fig. i is a side elevation of those portions of the apparatus which arerelatively stationary path of the larger particles, or by envelopingline I particles of sand in globules of liquid to produce the results.noted. I Further objects of the invention have to do 1 with means forsuccessfully mixing the chemi- 'aboutoverthegrmindiikeastofieboat orm'ayshown at II is a conventional'commercial sand and by which the nozzle issupplied.

Fig. 2is aviewonanenlargedscaleshowing the nozzle apparatus largely inlongitudinal section.

Fig. 3 is a longitudinal valve which controls the supply nossle.

Fig.4isaviewtakeninsectiononlinel-l of Fig. 2. Y Fig.5 is a view takenin section on line 8-5 of Fig. 2. v I

Fig. 6 is an enlarged detail view-in axial sectionthrough the water pumpand metering arrangement.-

Figfllisaviewonanenlargedscaleinaxial section through the pneumaticallyoperated chemical pump and metering arrangement.

Like parts are identified by the same reference characters throughoutthe several views.

The apparatus shown in Fig. i k mounted for convenience on a base I,whichf may be pulled section through the be carried on the chassis of atruck. The device blast generator. It includes a large tank or hopper.ll within which the sand is contained, and a mixer I I in which thereis a cut-oi! valve (not shown) actuated by the control lever II. Air

. from the compressed air line Ills supplied subiect to the main controlvalve II to a pipe I.

which leads to the generator. a portion of the of liquid to the" trolcut-oil valve ll and a check valve ll.

2", through the hose 2 with the sand blast hose 2|.

The metering valve m is of the type which may either be shut oi!completely oropenedonly to a predetermined and very slight extent.Because of the introduction of water into the nozzle in the mannerhereinafter to be described, the water might accumulate in the nozzleand mix with sand therein to cause the sand to cake and stop the nozzleii it were not for this by-pass which, eventhough the valve controlledby lever ll may be momentarily closed, will nevertheless permit asufficient quantity of air to flow through the hose 20 to keep thenozzle open and to keep the water moving toward the nozzle discharge.

On a separate sub-base 22 are mounted a pressure tank 23, thepneumatically operated water metering pump 2|, the pneumatically oprated chemical metering pump 25, and the chemical storage tank 28.

The water supply pipe 21 communicates with the chemical storage tank 2!by means of valve 20 only for the purpose of facilitating the filling ofthe chemical tank for the dilution of the chemicals placed therein. Themain purpose of the water connection at 21 is to supply'the pump 24 bymeans of pipe 2! with whichpipe 21 communicates subject to an automaticpressure concut-oi! valve 22 is self-closing and is held open only bythe pressure of air admitted to its con- The trol chamber 32 throughpipe 32 from the air I supply pipe 3| which communicates with the mainair pipe ll. When the main control valve II is cut oil, the water valvell closes itself. When the control valve II is open, the air pressurealso opens the water valve to leave theapparatus in condition foroperation.

Pipe 24 not only supplies the control chamber 32 01' the automatic valvell, but also supplies the pressure tank 28 and the pump by means ofpipes II and l! respectively, both of which are subject to the controlof the regulating or reducing valve 31. The valve Il may be adiusted toa fixed setting which will automatically compensate or equalizepressures according to the hose lengths and sizes of hoses used in theapparatus to arrive at a negative pressure or partial vacuum at thepoint where the liquid enters the gun at 81. Pipe 2! is provided with anormally closed cut-oi! valve which is only opened to build up asumcient'head or air in the top of tank 23 a ainst which the water andchemical admitted to the tank may operate.

The pump 24, shown in detail in Fig. 6, is likewise of conventionalcommercial design and hence will be described but briefly. In additionto the air admission pipe it and the water admission pipe 20 previouslydescribed, the pump has a. pipe 3. communicating with the chemical pump25 and a pipe SI which serves as an airdischarge pipe and which, for thepurposes of this invention. leads to a point below the surface of thechemicals in tank 2|. such tank being i'reely vented to the atmospherewhereby the air cscaping through the submerged outlet ll aerates andmixes the chemicals.

The construction and operation of the pneumatically driven water pumpare as follows:

In the control head 4. is an air exhaust valve ll and an air inlet valve2 mounted on the same stem 0 and connected with a diaphragm M. Thediaphragm has its opposing faces exposed to the chambers 48 and 46respectively. Chamber 46 communicates through duct II with the dis-Icharge conduit 48 which-leads to the air exhaust pipe 38. Thesamechamber II at the right hand side of the diaphragm as viewed in Fig. 6communicates through a duct 49 with a tubular post 50 and thence subjectto the control of valve II with the interior of the pump chamber 82. 4

The float i3 reciprocates on the guide post 5.. At its lower extreme ofmovement it operates the lever 54 which opens valve ll, the valve beingclosed by spring 55. At its lower extreme of movement the float 53 alsoengages a ring it connected by link 51 with lever 58 which displaces theball valve 59 which is normally seated by gravity to cut oflfcommunication between the pump chamber 52 and the diaphragm chamber all. Diaphragm chamber 45 has restricted communication through theannular clearance around the valve stem 43 with the inlet chamber 80.-

through pipe 28 subjectto the control of check valve n, the float willhe in contact with lever '58 which will thereupon be displaced to permitthe seating of valve 59. When valve 59 is closed the air leaking aroundthe valve stem from inlet chamber into diaphragm chamber ll will act onthe diaphragm in a direction to seat the air exhaust valve II and toopen the air inlet valve 42, thereby letting air flow from the supplypipe 38 into the water chamber 52 through duct ii.

The air pressure exerted on the surface of the water will expel thewater from chamber 82 through the water discharge pipe 82, therebylowering the float II. In the lowermost position oi. the float the floatwill open valve ll and valve II as above described, thus permitting thepressure in the tank or chamber 82 to pass upwardly through'the post IIinto diaphragm chamber 40, thus equalizing the pressure in the diaphragmchamber 40 with that in chamber 48 and permitting the air pressure onthe exhaust valve to displace the valve assembly-to a position where.the inlet will be closed and the outlet valve U will be open. The watersupply under pressure through pipe 21 will now open the check valve 3|and enter the bottom of tank I2, thus displacing the air therefromthrough duct ii and discharge pipe 32, raising the float to the pointwhere the cycle will be repeated in the manner above described. N

As previously indicated, the air discharged from the pump throughexhaust pipe 30 is used elevated position as shown in Fig. "1. Pipe acommunicates with the air cylinder CI- above piston l' l. Bothcylinders. between the respective pistons. are vented through duct II.The chemical from tank 28 is admitted through pipe The chamber a: beingfull of water admitted 12 subject to the control of a check valve 18 andis discharged through pip I4 subject to the control of a check valve I8,pipe 14 leading to the outlet pipe 82 from the water pump and thencecommunicating through pipe 16 with the pressure tank 28.

In actual practice the water pump displaces 2 gallons of water in eachoperation and the chemical pump 25 displaces /4 pint of chemical in eachoperation. It will, of course, be understood that the water pump 24 maybe used for pumping any suitable solvent or rust resistin chemical, theterm "water being used herein for the purpose of description and not oflimitation.

It will be apparent from the foregoing that the operation of thechemical pump is entirely automatic, being controlled by the operationof the water pump. When air is admitted to the water chamber 52 to expelthe water therefrom, the air pressure is communicated through pipe 88 tothe air cylinder 85 of the chemical pump, thereby forcing piston 61downwardly whereby piston 68 expels the charge of chemical from thedisplacement cylinder 88 of the chemical pump. Thus the chemical and thewater flow together from pipes 82 and 14 respectively, into pipe 18 andthence to the storage tank 23 where the mixture is stored under a headof approximately 20 pounds more or less of air which is confined in thetop of said tank.

When the exhaust valve 4| in the water pump is opened to relieve thepressure of air in tank 82, the pressure on piston 81 of the chemicalpump is likewise relieved through pipe 38, whereby the spring 18 liftsthe piston assembly in the chemical pump to introduce a fresh charge ofchemical through pump 12 and check valve 13 into the displacementcylinder 88.

From the bottom of the storage tank 23 the liquid line 11 leads to anatomizing fitting in the nozzle subject to the control of a diaphragmvalve 18 which is shown in detail in Fig. 3. While this valve is ofconventional manufacture it is important to use a valve of this generaltype because no other valve has been found to be as satisfactory and asfree from clogging in a device where sand is used. This valve has aninlet passage at 18 and a discharge passage at 18' ber tween which thereis a partition at 88 upon which the diaphragm 8| may be forced to seatby the pressure member 82 actuated by a screw 83.

The liquid supplied through pipe 11 subject to the control of valve 18is admitted through a ported boss 84 to the interior of the handleportion 85 of the nozzle. Within this handle, in registry with the boss,is a sleeve 88 having an annular peripheral channel coacting with thetube of the handle to comprise a closed passage through which the wateris distributed to the various orifices at 81 through which the water maypass sleeve 86 into the annular mixing chamber at 88.

.A special fitting at 88 is secured in the end of sleeve 88 and has astem portion 8| projecting centrally through sleeve 88 to guide the sandblast therethrough. The inner bore 82 traversed by the sand blast iscounterbored at 85 to provide a tapered inlet. Externally the fitting istapered near its discharge end at 88. The diameter of this bore will bevaried according to the size of the nozzle. Roughly its cross sectionaldiameter is approximately twice that of the nozzle. For example, I use afitting with a /4" bore when I employ a nozzle, and I use a fitting witha /8" bore for a $41 to 1%" nozzle.

The nozzle proper as indicated at 81, is of generally conventionaldesign. It is, however, provided with a, novel arrangement forinterchangeably mounting it on the handle tube 88. For this purpose thenozzle stem 88 is Provided with a flange 88 having an externalperipheral diameter adapting it to fit reasonably closely within thehandle tube 85. At its end the handle tube is provided with an annularnut I88 and between this nut and the flange 88 I interpose a rubbersleeve |8| which is placed under compression when the nut is turned upupon the end of tube 85. The rubber sleeve not only holds the nozzlestem 88 in position, but also serves as a packing to prevent leakagewhile permitting an immediate change of nozzles. It is not evennecessary to use tools, for the pressure which can be exerted intightening the nut I88 by hand is entirely adequate to hold the nozzlein place and to distort the rubber packing |8| in such a way as to packthe device adequately. The internal bore through the nozzle stem 88 iscounterbored to provide a tapered inlet or mixing chamher at I82 whichis maintained in the proper desired relationship to the tapered end 88of fitting 8| by the pressure contact of flange 88 with the end ofsleeve 86. The air and sand passing across the gap between fitting 8|and the nozzle stem 88 aspirates into the stream the mist of chemicallytreated water which has been delivered through the fine apertures 81into the annular space at 88.

As previously explained, throughout the period when the device is in usea small amount of air by-passed through the hose 2 is continuallyflowing through the nozzle whether or not the main stream of sand andair is flowing. This relatively small amount of air is suflicient tokeep up the aspiration of water from the annular passage 88 under allcircumstances, thus preventing any accumulations of water within thehandle and also tending toprevent sand from clogging the water passages.

By introducing the chemical into the pneumatically carried stream ofsand prior to the discharge thereof, I ensure the thorough comminglingof the chemical with the sand carried by the blast so that each particleof sand is believed to be a carrier for the chemical at the time ofdischarge, thus ensuring the treatment of the sand blasted surface withthe chemical at the very instant when it is cleaned.

The protective or rust inhibiting chemicals may be varied according tothe requirements of the work. For cleaning steel forgings or castingsand for much other work I have used with great success a chemicalpreparation made up by using in every 100 gallons of water in thechemical tank 3 to 5 ounces of the following preparation:

Pounds Trisodium phosphate 100 Zinc oxide (this being used only wherethe water supply is alkaline) 2 Neutral sodium dichromate (more beingused for painting old steel and less for new steel) 4 to 6 Leadphosphate 1' Chemically pure lime (less being used for new steel thanfor old steel) 6 to 10 Using a nozzle a device made in accordance withthe present invention will discharge approximately 450 lbs. of sand perhour in 80 cubic feet of air per minute at 90 lbs. air pressure but itwill only require gallons of water or rust-inhibiting liquid, or less,in an hour.

As compared with pneumatic sand blasting as heretofore known, this smallamount of water or rust-inhibiting liquid is adequate to lay the dust,thus substantially completely removing the danger of silicosis. In sodoing it renders the blast much more effective. The sand ordinarily usedin sand blasting averages approximately $7.50 per ton in cost. With theapparatus herein disclosed it is possible to use cheap sand atapproximately $2.50 per ton with equal or better results. As abovenoted, I' ascribe the improved results in part to the fact that thewater apparently adheres to the dust particles, possibly giving themincreased momentum but more probably removing them completely from theblast and preventing them from cushioning the cutting action of theheavier and sharper particles.

At the same time the amount of water or rustinhibiting liquid used isnot such that the disposal of waste is a problem. The chemicals arecarried to the work and left on the surface without being washed away bysluicing quantities of water. Where such small quantities of water areused it is feasible to incorporate chemicals in the sand blast, whereasotherwise it would not be feasible to do so, because the cost would beprohibitive. By mixing the chemicals with the sand blast I ensure thetreatment of the surface at the instant when the scale is removed, thusleaving no interval of time between the cleansing and polishing of thesurface and the treatment thereof to prevent oxidation. This leaves amuch brighter and more permanently rust free surface than has heretoforebeen possible to achieve.

My improved apparatus has been used in the Far West where water isscarce, and there also the small quantity of water used is significant.While the device actually uses in the neighbor hood of 15 gallons ofwater per hour when a 1%" nozzle is employed, I should regard gallonsper hour as being a small quantity for such a nozzle within the meaningof the aforesaid description. A greater quantity would create disposalproblems, be wasteful of chemicals, and make the chemical treatment lesseffective. It will, however, be understood that in reference to theamount of water discharged from the nozzle 1 am referring to thechemically treated water as stored under pressure in tank 23.

It will be apparent to those skilled in the art that my process does notinvolve hydraulic sand blasting as that term has previously been known.The small amount of water used is merely a fine mist and the compressedair is still relied upon to furnish the impetus by which the sandblasting operation is conducted.

The sand blasting method herein disclosed constitutes an improved meansof cleaning and cutting viscous surfaces. It is adapted to clean lightgauge or frail metal parts without warping or buckling thereof, andavoids the generation of heat in the cleansed articles such as commonlyresults from dry sand blasting thereof, this being particularlyimportant where the treatment is applied to a surface of viscousmaterial which would soften and run when heated.

My improved treatment is also important in completely removing foreigngreases or oils from the articles being treated, and in scouring thesurfaces of such articles while at the same time leaving such articlesfree of rust for substantial periods so that they do not requireimmediate painting for their protection. My improved method is furtheradvantageous in that it is successfully used on wet surfaces withoutrequiring the preliminary drying of such surfaces as has heretofore beennecessary in ordinary pneumatic sand blasting.

My improved method is further advantageous in the cleamng of concrete sothat new concrete work added thereto will result in a. stronger andwater-tight bond or union.

The abrasive, including the dust therein contained, is confined bythemoisture to the immediate vicinity of the work and does not float inthe air but drops to the ground about the work and stays there.

I claim:

1. In a sand blast system, the combination with a sand blast generatorand an air supply pipe therefor provided with a control valve, of aconnection to said pipe controlled by said valve, a water supply pipe, achemical supplymeans, and pumps provided with operating means actuatedby said air connection for operation to deliver water and chemicals inpredetermined quantities when said valve is open, and means fordischarging said water and chemicals with a sand blast from saidgenerator.

2. Sand blast apparatus comprising the combination with a sand blastgenerator, a nozzle, and means including a hose affording communicationbetween the generator and the nozzle, of means including an aspiratingdevice for introducing a liquid into said last mentioned means in theproximity of the nozzle, a liquid supply tank, a chemical meter providedwith means for delivering chemical to the liquid supply tank, and meansfor pneumatically operating said meter, said pneumatic operating meansand said generator having a common source of air supply and a commoncontrol valve.

3. Sand blast apparatus comprising the combination with a generator anda nozzle, of a water pump, a chemical pump, means for the pneumaticoperation of said pumps, means for delivering the eflluent of the pumpsto the sand blast in proximity to the nozzle, an air supply common tothe generator and the means for pneumatic operation of the pumps, awater connection to the water pump, and valve means controlled by saidair supply for opening said water connection to said pump when said airsupply is elfective to actuate the water pump.

4. Sand blast apparatus, comprising the combination with a manuallycontrolled source of elastic fluid supply, a mixing nozzle provided witha main inlet and auxiliary atomizing inlets, a receiver for abradingmaterial, a mixing chamber associated with the receiver and adapted toreceive sand therefrom, manually controlled means for directing theelastic fluid to the nozzle either through the receiving and mixingchambers or through a by-pass, and means for delivering chemicallycharged liquid through the atomizing inlets of said nozzle, whereby saidliquid may be utilized for coating particles of sand entrained by theelastic fluid delivered through said nozzle, and for charging theby-passed elastic fluid with rust resisting chemical material.

5. In a sand blasting apparatus provided with a sand container, anassociated mixing chamber and a nozzle, the combination therewith ofvalved pipe connections adapted for delivery of an elastic fluid underpressure to the sand and mixing chamber, and means dependent uponelastic fluid delivery through said pipe connections for charging waterwith a rust resisting chemical and jetting it into said nozzle inpredetermined proportions to the film of elastic fluid passingtherethrough.

6. In a sand blasting apparatus provided with a sand container, anassociated mixing chamber and a nozzle, the combination therewith ofvalved pipe connections adapted for delivery of an elastic fluid underpressure to the sand and mixing chamber, means dependent upon elasticfluid delivery through said pipe connections for charging water with arust resisting chemical and jetting it into said nozzle in predeterminedproportions to the film of elastic fluid passing therethrough, andvalved by-pass connections for delivering the elastic fluid to thenozzle and water supply means independently of delivery of sand from thesand container and the mixing chamber.

7. The combination with a pneumatically operated sand blasting apparatushaving an air inlet pipe, an outlet .pipe provided with an aspiratingnozzle and an associated blast nozzle for delivery of air and sand to asurface to be cleaned, of pneumatically operable pumping mechanismadapted for delivery of chemically charged liquid to the aspiratingnozzle, said pumping mechanism having power connection with the airinlet pipe, whereby the pumping mechanism may be automatically operatedduring sand blasting operation.

8. A combination as set forth in claim 7, in which the pumping mechanismhas its outlet connected with an annular series of atomizing nozzlesleading through the wall of the aspirating nozzle to the annular spaceabout the sand blast, and adapted to atomize the liquid chemicalpreparatory to its exposure to the suction of the aspirating nozzle andmixture with the sand passing through such nozzle.

9. Sand blast apparatus, comprising the combination with a sand blastinggenerator, a mixing nozzle and a pipe connection between the generatorand the nozzle, of means for metering and supplying to the mixingnozzle, under pressure, atomized liquid charged with rust resistingchemical material in predetermined quantities substantially equal tothose required for coating the particles of sand generally with suchmaterial, whereby the surface to be cleaned may be coated with thechemical material simultaneously with the impact of the sand particlesthereon.

10. A sand blasting process, consisting in gencrating a dry sand blast,metering, pumping and uniformly distributing quantities of liquid rustresisting chemical material to the particles of sand in particle coatingproportions immediately prior to contact of the blast with the surfaceto be cleaned.

11. A sand blasting process, consisting in generating a dry sand blast,metering, pumping and atomizing quantities of liquid rust resistingchemicals into the sand blast in definitely predetermined proportions tothe volume of the blast, and in quantities substantially equal to thoserequired for coating the surface against which the blast is projected.

V ARTHUR H. EPPLER.

